why has my evergreen grass seed not grown yet in a week

In UK it would of got washed away or cold!
But it may be because you havent watered enough in any dry spells.
Thats only reason i can think off

Make sure the seed is stillpresent - hasn't been washed away by the rain. If it has, reseed, cover with clear plastic if possible till you see the first signs of germination, then remove the plastic. Otherwise, another week should do it.